Arachidonic acid and a few other polyunsaturated fatty acids are bio activated in humans by enzymatic oxygenation to prostaglandins, leukotrienes, epoxides (EETs) and other local hormones, which contribute to fever, pain, inflammation and cancer development, and to regulation of physiological processes during reproduction and in many other organs. Common drugs such as aspirin, acetaminophen (paracetamol) and ibuprofen inhibit biosynthesis of prostaglandins and reduce symptoms of disease, but may also cause side effects related to their actions. Other drugs are based leukotriene receptor antagonists (e.g., montelukast), which are use for treatment of bronchial asthma. Bioactivation of polyunsaturated fatty acids also occur in plants and fungi where oxygenation of linoleic and linolenic acids is important for the plant-pathogen interaction and for fungal reproduction and pathogenicity. The goal of our research is to investigate the mechanism of oxygenation and bioactivation of fatty acids and to determine their biological function.
We investigate mainly three groups of enzymes: (i) lipoxygenases, (ii) cytochromes P450 and (iii) heme-containing dioxygenases. These enzymes occur in man but also in important fungal pathogens, e.g., Aspergillus fumigatus causing farmer´s lung disease and Magnaporthe grisea, causing rice blast disease and destruction of 25% of the rice crop of Japan. Our goal is to understand how the enzymes work in order to understand their physiological and pathophysiological functions and to develop new drugs.
In humans, the prostaglandin endoperoxide, PGH2, can be transformed by cytochromes P450 to thromboxanes, prostacyclin and to 19-hydroxy-PGH2, the precursor of 19-hydroxy-PGE2. The latter is the main prostaglandin of human seminal fluid and occurs in high concentration in human semen, where it is formed by CYP4F8 of the seminal vesicles. CYP4F8 and CYP4F22 are also expressed in skin and we investigate their oxygenation of fatty acids.
All lipoxygenases contain a catalytic metal, iron in humans and plants. We focus our basic research on the first described manganese-lipoxygenases, which are important for Gäumannomyces graminis, an important pathogen of wheat, and its structurally similar lipoxygenases of Magnaporthe grisea, and Aspergillus fumigatus. These fungi also contain oxygenate cyclooxygenase-related enzymes, which oxidized linoleic acid by to a series of vicinal diols (5,8-dihydroxy-, 7,8-dihydroxy-, and 8,11-dihydroxyoctadecadienoic acids) via formation of hydroperoxides (8-hydroperoxy- and 10-hydroperoxylinoleic acid), which likely function as sporulation hormones. The reaction mechanism and identification of these diol synthases are described in our recent papers in The Journal of Biological Chemistry. Site-directed mutagenesis of 7,8-LDS revealed structural and mechanistic similarities to cyclooxygenases. A novel observation is the allene oxide synthase of A. terreus.
Principal investigator: Ernst H. Oliw